Heading in reverse: Toll road debt grows to almost $19 million a mile

As the economy continues creeping along in the slow lane, drivers will probably decide against paying the toll.

As a consequence, and somewhat ironically, toll roads and bridges may become even more expensive for travelers in an effort to pay down billions in debt.

A new report from Moody's Investor Services concluded toll road numbers in 2012, on the whole, looked similar to those in 2011. But that could change, Moody's warns, as toll road agencies add debt.

Debt per road mile increased to $18.9 million in fiscal 2012, from $14.3 million in 2011, the report found.

"Steady toll rate increases will be necessary to support a growing debt burden," explained Moody's, "although the unfettered ability to increase toll rates could face mounting political pressure in an economy that is growing slowly."

Moody's said modest growth in toll road and bridge use was enough to offset growth in debt in 2012. But for the rest of 2013, the outlook for toll roads remains negative.